The present invention relates generally to a method for communication among a plurality of devices, such as input/output (IO) devices, in a network, such as a control/monitoring automation network. In particular, the present invention relates to establishing a network identity for each device.
A local area network such as the Ethernet, can be used with a control system for industrial applications. Such a control system can be used to enable controllers, host computers, control devices such as variable frequency drives, and other devices to communicate throughout the control system. The devices connected together in such a communication link are generally referred to as xe2x80x9cnodes.xe2x80x9d Each node has a unique network identifier, i.e., Media Access Control (MAC) address, that facilitates network communication between the nodes.
In an automation factory where a plurality of automation devices or input/output devices are used to perform a variety of intended functions, each device has a controller, such as a programmable logic controller (PLC), to communicate with a controlling workstation or the PLC of another automation device. Furthermore, the PLC includes a software program to control the network device in performing the intended function. It is quite common to place network devices at physical site locations in accordance with their particular functions. Conventionally, each of the network devices is identified by the MAC address (or an Internet Protocol (IP) address) associated with the device. The network identifier is a fixed address which is given to a device when it is manufactured or assigned by a user during interconnection with a network. The identifier, or MAC address, is unrelated to the physical site location of the device in the network.
If a PLC or other network device at a specific network location is replaced by another PLC, the replacing PLC will not be operably connected to the network until its MAC address replaces the removed PLC""s MAC address in the control system""s application. This network address constraint is disadvantageous in factory automation settings. For instance, if a problem arises with a network device, maintenance must be performed by professional personnel skilled in networking management to administer implementing the new MAC address. This level of involvement in network support is costly and time consuming. It is therefore advantageous and desirable to provide a method and a control system wherein the need for maintenance of the network by professionally skilled personnel is reduced or eliminated.
The present invention is provided to solve these and other problems.
A first embodiment of the present invention is directed to a method of identification of a network device based on the physical location of the network device. The method comprises the steps of identifying the physical site location of a network device and associating the physical location to the device address so as to allow the device to communicate with other devices in the network.
Another aspect of the present invention is a control system having a plurality of devices, wherein one or more devices include means for identifying the physical location so that the physical location is used as an identifier of the device in order to allow the device to communicate with other devices in the system. Preferably, a software program is used to convert a map of physical locations of the devices into an address table required for routing messages to the devices.
A further aspect of the present invention is a device to be used in a control system wherein the device includes means for identifying its own physical location so that the physical location can be used as a network identifier, i.e., address, of the device in order to allow the device to communicate with other devices in the control system.